Sequential latent effects of a sub‐lethal dose of ivermectin in Calliphora vomitoria L.

A single sub‐lethal dose of 0‐3 μg ivermectin applied topically to third (last) instar larvae of Calliphora vomitoria prevents a significant number of adult flies from escaping from their puparia after metamorphosis, although the flies show no signs of physical abnormality. Of the insects that manage to emerge, a significant number of females do not develop mature oocytes. Ivermectin in sub‐lethal doses seriously impairs post‐embryonic development in Calliphora at four independent levels: interference with pupariation, suppression of adult head development, inhibition of emergence from the puparium, and disruption of ovarian development in the adult female. These findings are discussed in relation to ivermectin's efficacy as a pesticide and particularly to non‐specific effects upon dung‐inhabiting insects.